1. Field of the Invention
The present invention pertains to a system for traversal through a fluid transmission pipeline for providing a selected isolated or sealed space within a section of the pipeline and for pressure testing the pipe section which defines the sealed space.
2. Background
Fluid transmission pipelines occasionally require modification or repair as well as periodic pressure testing to inspect the structural integrity of the pipe or to locate suspected leaks. Examples of prior art pipeline testing apparatus comprise the devices described in U.S. Pat. Nos. 3,483,895 to Barto, 3,690,348 to Patterson, 3,834,422 to Larson and 4,602,659 to Parkyn. The devices described in all but the Larson patent require the use of two unconnected devices for isolating a section of pipeline for pressure testing or the device must be used in conjunction with a pipeline valve at a particular location which already exists in the pipeline to isolate the test section. In this latter instance, a significantly long section of pipe may be required to be pressurized for the test procedure and the complexity of using two separate line blocking "valves" as described in these references is difficult to manage in many instances.
One approach to overcoming the problems remaining unsolved by prior art apparatus is described in a U.S. patent application entitled: "Apparatus For Pressure Testing Pipelines", Ser. No. 07/253,781, Filed Oct. 5, 1988 in the name of Lloyd A. Baillie and assigned to the assignee of the present invention. Although the device described in the aforementioned patent application presents a unique solution to isolating a relatively modest length of pipeline section to be pressure tested, there are instances wherein the curvature of the pipeline or the section length is unsuitable for the accordion or bellows type structure of the Baillie device.
Accordingly, there has been a need to provide an improved seal system for isolating a section of pipeline of selected length for modification or repair and for pressure testing that section by seal devices which are remotely controllable and which are operable to be used in tandem and connected to each other so that a defined section of pipe is isolated. It has also been deemed desirable to provide a pipeline pressure test system which does not require the use of an existing pipeline valve and which may be remotely controlled to pressurize the pipeline section in question, relieve pressure from that section upon completion of the test and reposition the means effecting sealing of the pipeline to a new section for testing.